Short answer: When using 4H (four-wheel drive high), there isn’t a universal legal maximum speed, but riding the line between traction and drivetrain wear matters. Most manufacturers and experienced enthusiasts advise staying well below highway speeds and using 4H primarily for low-traction conditions (snow, mud, light off-road). Typical practical guidance is to keep speeds around 30–50 mph (50–80 km/h) or lower depending on the vehicle and surface, and to avoid sustained high-speed driving in 4H on dry pavement. If you’re on pavement and conditions allow, you’ll generally be safer and more efficient staying in 2H and using 4H only when needed. Details and practical guidance

• Purpose of 4H: 4H engages all four wheels for improved traction on slick or loose surfaces (snow, slush, sand, gravel) or when extra grip is needed on uneven terrain. It is not intended for high-speed highway driving on dry pavement, where steering feel and drivetrain stress can increase.

• Engaging and speed considerations: Many manuals specify that you can shift between 2H and 4H at moderate speeds (often up to around 60 mph or so in some vehicles) but disengagement and shifting guidelines emphasize avoiding abrupt changes or engaging 4H on dry pavement at high speed. The consensus across sources is to avoid high-speed use of 4H on dry surfaces and to slow down when traction changes demand 4H.

• Real-world ranges: Community answers and vehicle-specific guidance typically place a practical ceiling for 4H use on mixed surfaces in the 30–40 mph range, with allowances up to 50 mph in some cases depending on vehicle design and road conditions. Beyond that, the benefit of 4H diminishes and risk of drivetrain binding or handling issues increases.

• 4L (low range) is a separate, much slower mode intended for extreme terrain; it should be used well below 25–30 mph in most vehicles. This is not a substitute for highway speeds and is explicitly for low-speed, high-torque scenarios.

What to check for your specific vehicle

• Owner’s manual: Look up the recommended operating ranges for shifting between 2H and 4H, and any speed limits or cautions for your exact model and transfer case. Manufacturer guidance varies by make and model, and the manual will give you the official limits.

• Surface and load considerations: On snow or ice, moderate speeds with careful handling are appropriate; on loose gravel or deep mud, lower speeds help maintain traction without overstressing components. Avoid sudden throttle changes and abrupt steering inputs in 4H.

Bottom line

• You can drive in 4H, but it’s not designed for high-speed highway driving. Use 4H at lower speeds where traction is compromised, typically around 30–50 mph (50–80 km/h) or less, depending on conditions and vehicle. If highway speeds are needed, switch back to 2H when conditions permit, and always follow your vehicle’s manual for the safe operating range.